Sialic acids are known to be widely distributed in nature, and are physiologically functioning important substances.
Sialic acids have been reported to possess various functions including intercellular recognition, infection preventing activity, controlling immunological functions, myopathy amelioration, and hair growth or restoration (Non-patent Documents 1-3).
Furthermore, sialic acids are known to promote the production of insulin-like growth factor 1 (IGF-1) (Non-patent Document 3). And IGF-1 is known to have a hair restoring effect (Non-patent Document 4) as well as an action for enhancing skin elasticity (Non-patent Document 5).
In the case of oral administration, the pharmacological/biological activities of sialic acids are known to be such that sialooligosaccharides that are sugar chains containing sialic acids are more active than free sialic acids (Non-patent Documents 1 and 2, as well as Patent Document 1).
A number of methods for producing such sialooligosaccharides have been reported and they include: a method involving purification by organic solvent extraction method and active carbon column chromatography from milk that has been freed of lipids and proteins (Patent Document 2); a method involving purification by ultrafiltration and gel filtration chromatography from milk or a dairy product that has been freed of lipids and proteins (Patent Document 3); a method involving purification from lipid- and protein-free whey by ion exchange resin (Patent Document 4); a method of production from defatted bird egg yolk by extraction with water or a salt solution, or ultrafiltration of a solution obtained by such extraction with water or a salt solution, or enzymatic digestion of a solution resulting from such extraction with water or a salt solution (Patent Document 5); and a method in which cytidine monophosphate-sialic acid is reacted with a sugar chain in the presence of a sialic acid transferase and phosphatase to transfer the sialic acid to the non-reducing terminal of the sugar chain (Patent Document 6).